This time around, he’s evaluating the Apple Watch’s sapphire-coated screen with a diamond tester and comparing it to the Apple Watch Sport, LG’s G Watch R, the iPhone 6 and a high-end analog watch by Tissot, which uses sapphire for protection.

He came away fairly impressed with Apple’s sapphire, concluding it does match those of classic sapphire watches. Sapphire, for those wondering, is the second-hardest transparent substance after diamond. Have a look at the video and tell us what you think in the comment section.

By the way, he used a $12 diamond tester purchased on Amazon.

The gadget basically determines the conductivity of various materials and is used mostly for evaluating jewelry and precious gemstones like diamonds.

While standard glass doesn’t give a reading with the diamond tester, sapphire is a very conductive material and typically gives a readout of about 7 or 8 on the scale. So how did Apple’s sapphire fare in this test? Is Apple’s a legitimate sapphire crystal?

“To ensure a precise fit for the case, the crystal is cut using a diamond-encrusted wire. To make room for an integrated antenna, a tiny groove is laser-ablated around its perimeter. And to create the smoothest possible finish, the crystal is polished with diamond-covered pellets.”

Unbox Therapy gained worldwide fame — or notoriety, depending on your point of view — with a widely circulated and reblogged stress-test video showing the iPhone 6’s bend-ability, which then sparked the whole Bendgate nonsense.